The present document relates to a camera module.
A camera module is a device for photographing an image. The camera module may be provided in a mobile terminal in order to diversify applications of the mobile terminal. Here, the mobile terminal includes not only mobile phones, but also various wireless communication devices.
A camera module in the related art includes a lens unit, a lens holder, a housing, an IR cut-off filter, an image sensor and a printed circuit board. The lens unit receives an optical image of a subject and then transfers the optical image to the IR cut-off filter. Upon receiving the optical image, the IR cut-off filter cuts off infrared ray from the optical image and then transfers the optical image to the image sensor. The image sensor converts the optical image into an electric signal to output the electric signal. The printed circuit board is formed with predetermined electric patterns and a plurality of electrodes. The printed circuit board digitalizes the image signal output from the image sensor.
Focusing is performed by adjusting the distance between the lens unit and the image sensor to provide the clear image. The lens unit is coupled with the lens holder. Female/male screws are formed at coupling portions of the lens holder and the housing, respectively, so that the lens holder can be screw-coupled with the housing. That is, the focusing is performed by adjusting the distance between the lens unit and the image sensor using the screw mechanism.
According to a camera module in the related art using the screw mechanism, a worker sets the focal distance by rotatably coupling the lens holder with the housing using predetermined equipment. Therefore, if the torque value between the screw sections of the lens holder and the housing is out of a predetermined reference value, following problems may occur.
That is, if the torque value is less than the reference value, the lens holder cannot be securely coupled with the housing. In this case, the lens holder is randomly rotated when coupling the lens holder to the housing, causing the defocus phenomenon.
In addition, if the torque value is higher than the reference value, the focal distance can be precisely adjusted by rotating the lens holder. However, impurities are produced due to friction between the screw sections of the lens holder and the housing. Such impurities may degrade the image quality.